This invention relates generally to refrigeration system alarm apparatus and more particularly, but not by way of limitation, to monitoring and control apparatus which detect power outages and excessive temperatures in a food refrigerator or freezer.
When refrigerating or freezing food, one must be careful to insure that safe refrigerating or freezing temperatures are maintained to prevent food spoilage and loss due to excessive temperatures. Without some type of alarm device, this task of insuring safe operating temperatures can be difficult because defects which might cause such excessive temperatures might go unnoticed for periods of time during which the refrigerated or frozen food will spoil. These defects can arise from electrical or mechanical failures which are not readily detectable by one who only periodically opens the refrigerator or freezer to put in or take out food. Furthermore, when one opens the refrigerator or freezer, the door can be left ajar whereby the interior temperature can become excessive.
In addition to insuring that safe operating temperatures are maintained in a refrigeration system, it is also important to insure that the refrigeration equipment is properly operated to prevent equipment damage which might cost hundreds or thousands of dollars to repair. One type of equipment damage is that which may be caused in a compressor which is improperly actuated at a time during which the compressor has substantial internal pressure differentials. For example, the compressor might be operating with substantial internal pressure differentials when power to the compressor is lost. If power were relatively quickly restored and reapplied to the compressor, the compressor might be damaged through this rapid restart with the internal pressure differentials.
Therefore, there is the need for a device which monitors a refrigeration system to detect temperature and power anomalies, to give an alarm signal when such anomalies are detected, and to automatically protect the refrigeration equipment, such as the compressor, when such anomalies occur. Although many devices have been proposed to meet one or more of these needs, we know of no single device which meets these needs in the same manner as the present invention described hereinbelow.